Use Of Chlorophyll Fluorescence Research Articles

Detection of multi-nutrients deficiency in cereal plants by the use of chlorophyll fluorescence

Detection of multi-nutrients deficiency in cereal plants by the use of chlorophyll fluorescence

The Use of Chlorophyll Fluorescence as an Indicator of Predicting Potato Yield, Its Dry Matter and Starch in the Conditions of Using Microbiological Preparations

The paradigm shift toward ecological agriculture has spurred efforts to phase out the use of conventional pesticides, and researchers are actively seeking natural alternatives to replace these chemicals. Aim: This study aimed to introduce an innovative intervention to enhance potato yields in a non-invasive manner, thereby elevating the content of both dry matter and starch. Ultimately, this approach seeks to enhance the quality of raw materials destined for the production of potato-enriched products. A field experiment was conducted in central-eastern Poland that employed a randomized sub-block method within a dependent split-split-plot design replicated three times. The main factor was pre-planting treatments, which included the application of a microbiological preparation to seed potatoes for: (a) 10 min, (b) 15 min, and (c) no treatment (control). Another factor was the fourteen potato cultivars of different earliness groups. Qualitative analyses were carried out in laboratory conditions. The application of the microbiological preparation yielded positive outcomes on the physiological indicators of potato yield, while augmenting the production of dry matter and starch when compared to the control object. The analyzed cultivars had the most pronounced impact on both the content and yield of dry matter and starch, demonstrating a wide array of responses to pre-planting treatments that incorporated microbiological preparations. For the first time in studies concerning effective microorganisms, chlorophyll fluorescence analysis was employed. Alternative solutions in the form of employing microbiological preparations offer the potential to effectively substitute pesticides and synthetic fertilizers in potato production, consequently enhancing the quality of raw materials for food.

Monitoring weed mechanical and chemical damage stress based on chlorophyll fluorescence imaging.

Currently, mechanical and chemical damage is the main way to carry out weed control. The use of chlorophyll fluorescence (CF) technology to nondestructively monitor the stress physiological state of weeds is significant to reveal the damage mechanism of mechanical and chemical stresses as well as complex stresses. Under simulated real field environmental conditions, different species and leaf age weeds (Digitaria sanguinalis 2-5 leaf age, and Erigeron canadensis 5-10 leaf age) were subjected to experimental treatments for 1-7 days, and fluorescence parameters were measured every 24h using a chlorophyll fluorometer. The aim of this study was to investigate the changes in CF parameters of different species of weeds (Digitaria sanguinalis, Erigeron canadensis) at their different stress sites under chemical, mechanical and their combined stresses. The results showed that when weeds (Digitaria sanguinalis and Erigeron canadensis) were chemically stressed in different parts, their leaf back parts were the most severely stressed after 7 days, with photosynthetic inhibition reaching R=75%. In contrast, mechanical stress differs from its changes, and after a period of its stress, each parameter recovers somewhat after 1 to 2 days of stress, with heavy mechanical stress R=11%. Complex stress had the most significant effect on CF parameters, mainly in the timing and efficiency of changes in Fv/Fm, Fq'/Fm', ETR, Rfd, NPQ and Y(NO), with R reaching 71%-73% after only 3-4 days of complex stress, and its changes in complex stress were basically consistent with the pattern of changes in its chemical stress. The results of the study will help to understand the effects of mechanical and chemical stresses and combined stresses on CF parameters of weeds and serve as a guide for efficient weed control operations and conducting weed control in the future.

Use of Chlorophyll Fluorescence to Estimate Photosynthesis and Its Relationship to Vase Life of Cut Roses

Use of Chlorophyll Fluorescence to Estimate Photosynthesis and Its Relationship to Vase Life of Cut Roses

Флуоресценция хлорофилла в оценке воздействия соединений тяжёлых металлов на водные организмы

Fluorescent methods allow to improve the bioassays because of time effectiveness. These methods give information on chlorophyll concentration and plant photosynthetic apparatus activity in a short period of time. The aim of this study was to estimate the sensitivity of aquatic organisms to heavy metals using chlorophyll fluorescent methods. The test-organisms of different taxonomic categories were used, including thermophilic strain Chlorella vulgaris Beijer, aquatic plants Elodea сanadensis Michx. and Lemna minor L., crustacean Daphnia magna Straus. Fluorimeter “Foton 10” developed in SibFU was employed to measure prompt and delayed fluorescence (PF and DF respectively). The experiments revealed that copper ions affected DF of chlorella in 30 minutes, resulting in a 50% decrease of relative indicator of DF (RIDF) in the range of concentrations 0.005-0.01 mg/l of Cu2+. Measuring the DF of duckweed was less time-consuming compared to registration the changing of morphological parameters when the plants were exposed to heavy metals. Copper, cadmium, and nickel exposures were found to decrease the RIDF of duckweed by more than 50% at the concentrations of 0.17, 0.31, and 1.89 mg/l respectively. However, zinc had no significant effect on the RIDF of Lemna minor in the range of 0.1-8 mg/l of Zn2+ within 24 h of exposure time. The analysis of fluorescent parameters of Canadian elodea showed the possibility of using the plant as a sorbent during the bioremediation of aquatic environments from heavy metals. Registration of chlorophyll fluorescence allowed revealing the toxic effects of negligible concentrations of heavy metals in experiments with the feeding rate of daphnids. The median effective concentrations (EC50) were 0.002, 0.02, 0.4, and 0.25 mg/l of Cd2+, Cu2+, Zn2+, and potassium dichromate respectively. This makes it possible to obtain information on the effects of pollution in the early stages of exposure and in a shorter time. Thus, the use of chlorophyll fluorescence in biomonitoring the state of the aquatic environment makes it possible to more quickly respond to changes in the ecological situation in water bodies.

Biocontrol Potential of Sclerotinia sclerotiorum and Physiological Changes in Soybean in Response to Butia archeri Palm Rhizobacteria.

Sclerotinia sclerotiorum is a necrotrophic parasitic fungus that causes Sclerotinia stem rot (SSR), which is currently one of the most difficult agronomic crop diseases to control. A number of plants of the Brazilian Cerrado biome have been shown to be important sources of symbiotic microorganisms with biotechnological potential, so we decided to test the potential of bacteria isolated from the dwarf jelly palm, Butia archeri (Arecaceae) for the control of the pathogenic effects provoked by S. sclerotiorum. For this, we bioprimed seeds and evaluated the effects of this biopriming on the OJIP transient patterns prior to and following infection by the phytopathogen. Plants treated with the BA48R strain of Enterobacter sp., and in particular, those treated with the BA88R strain of Bacillus cereus presented the best results in terms of the loss/gain of the physiological and symptomatological variables evaluated. The plants bioprimed with BA88R presented high post-infection levels of total chlorophyll (33.35 FCIs) and chlorophyll a (26.39 FCIs), maintained a high Nitrogen Balance Index (NBI = 18.87), and synthesized low concentrations of flavonoids (1.39). These plants also maintained high levels of PIABS (1.111) and PITOTAL (1.300) following infection, and low levels of Di0/RC (0.602), which indicates that, in the presence S. sclerotiorum, the efficiency of the photosynthesis in the plants treated with these bacteria was less affected in the reaction centers, as confirmed by the negative amplitude recorded in the L band. The present study reconfirms the importance of the use of chlorophyll fluorescence for the diagnosis of disease and conditions of stress in crop plants, in addition to demonstrating the effectivenesss of the BA48R bacterial strain and, in particular, the BA88R strain on systemic resistance induction and suppression of S. sclerotiorum in Glycine max plants, with enormous potential for the development of more sustainable agricultural processes.

Induction of chlorophyll fluorescence use for assessment of functioning of Gentiana lutea L. plants photosynthetic apparatus in different conditions of culturing in vitro

Aim. To study the peculiarities of functioning of photosynthetic apparatus of Gentiana lutea L. plants in vitro under different light qualities and source of carbon in the composition of nutrient medium by using the induction of chlorophyll fluorescence (ICF) method. Methods. Chlorophyll fluorescence was determined in light-adapted leaves of cultivated in vitro G. lutea plants by use of PAM fluorometry MultispeQ. The parameters change of photosynthetic apparatus functioning of cultivated in vitro plants was assessed with regard to light qualities (Variant 1: light intensity – 85 W/m2, when different spectra combinations of blue-wave band (Еb) and green-wave band (Еg) and red-wave band (Еr) was 33% : 42% : 25%; Variant 2: light intensity – 100 W/m2, with wave bands of spectra – Еb : Еg : Еr = 25% : 27% : 48%) and the source of carbon (10 g/l of sucrose or 3 g/l of mannite) in the composition of nutrient medium МS/2 (MS medium with half amount of macro- and microsalts), supplemented with 0.1mg/l of kinetin. Results. It was established that G. lutea plants cultivated in vitro for 90 days in light conditions of Variant 2 had a quantum yield photochemical of PS ІІ 8.3 % higher in comparison to G. lutea specimens cultured in light conditions of Variant 1. The vitality value of Variant 2 plants was 23 % higher. Change of carbon source in the composition of nutrient medium from sucrose (10 g/l) to mannite (3 g/l) was both increasing the efficiency of functioning of photosynthetic apparatus of Gentiana lutea L. plants in vitro and activating their resistance mechanisms to water deficit. Conclusions. The ICF method use shows that functioning of photosynthetic apparatus of G. lutea plants in vitro depends different qualities light and source of carbon in the composition of nutrient medium.
 Key words: induction of chlorophyll a fluorescence, plants in vitro, Gentiana lutea L.

Effect of salt stress on photosynthesis and chlorophyll fluorescence in Medicago truncatula

In the present study, photosynthetic parameters including gas exchanges, pigment contents, and chlorophyll fluorescence, were compared in two contrasting local Medicago truncatula lines TN6.18 and TN8.20, in response to salt added to the nutrient solution. Plants were cultivated under symbiotic nitrogen fixation (SNF) after inoculation with a reference strain Sinorhizobium meliloti 2011, a very tolerant strain to salinity (700 mM NaCl), and grown in a controlled glasshouse. On one month old plants (with active SNF), salt treatment (75 mM NaCl) was gradually applied. Photosynthesis, assimilating pigments and chlorophyll fluorescence were monitored throughout the experiment during both short and long terms, compared to control (non-saline) conditions. A genotypic variation in salt tolerance was found; TN6.18 was the more sensitive to salinity. The relative tolerance of TN8.20 was concomitant with the highest photochemical quenching coefficient (qP) affecting the maximum quantum yield of PSII (Y); the real quantum yield (ɸexc) was the most affected in the sensitive line. Moreover, stomatal and PSII reaction centers activities differed clearly between the studied lines. We found that the effect of salinity on photosynthesis of M. truncatula was related to PSII activity reduction rather than to stomatal conductance limitation. Photosynthesis was reduced by the inhibition of CO2 assimilation caused by PSII damage. This was clearly estimated by the Y, ɸexc and especially by the quantum yield of electron transport of PSII (ΦPSII). Thus, on the basis of our results on the two local M. truncatula lines, we recommend the use of chlorophyll fluorescence as non-destructive screening method to discriminate susceptible and resistant legumes to salt stress.

Structural and functional disorder in the photosynthetic apparatus of radish plants under magnesium deficiency

Magnesium (Mg) is one of the significant macronutrients which is involved in the structural stabilisation of plant tissues and many enzymes such as PSII. The latter efficiency and performance were analysed, using chlorophyll (Chl) a fluorescence induction kinetics and microscopic images, to detect the changes in structure and function of photosynthetic apparatus of radish plants grown under Mg deficiency (Mgdef). Plants grown under Mgdef showed less PSII connectivity and fewer active primary electron acceptors (QA) oxidizing reaction centres than control plants. Confocal and electron microscopy analyses showed an increased amount of starch in chloroplasts, and 3,3'-diaminobenzidine (DAB)-uptake method revealed higher H2O2 accumulation under Mgdef. Prominent changes in the Chl a fluorescence parameters such as dissipated energy flux per reaction centre (DIo/RC), relative variable fluorescence at 150μs (Vl), and the sum of the partial driving forces for the events involved in OJIP fluorescence rise (DFabs) were observed under Mg deficiency. The latter also significantly affected some other parameters such as dissipated energy fluxes per cross-section (DIo/CSo), performance index for energy conservation from photons absorbed by PSII antenna until the reduction of PSI acceptors (PItotal), and relative variable fluorescence at 300μs (Vk). This work emphasises the use of chlorophyll fluorescence in combination with microscopic and statistical analyses to diagnose the effects of nutrients deficiency stress on plants at an early stage of its development as demonstrated for the example of Mgdef. Due to the short growth period and simple cultivation conditions of radish plant we recommend it as a new standard (model) plant to study nutrients deficiency and changes in plant photosynthetic efficiency under stress conditions.

Using Phenomic Analysis of Photosynthetic Function for Abiotic Stress Response Gene Discovery.

Monitoring the photosynthetic performance of plants is a major key to understanding how plants adapt to their growth conditions. Stress tolerance traits have a high genetic complexity as plants are constantly, and unavoidably, exposed to numerous stress factors, which limits their growth rates in the natural environment. Arabidopsis thaliana, with its broad genetic diversity and wide climatic range, has been shown to successfully adapt to stressful conditions to ensure the completion of its life cycle. As a result, A. thaliana has become a robust and renowned plant model system for studying natural variation and conducting gene discovery studies. Genome wide association studies (GWAS) in restructured populations combining natural and recombinant lines is a particularly effective way to identify the genetic basis of complex traits. As most abiotic stresses affect photosynthetic activity, chlorophyll fluorescence measurements are a potential phenotyping technique for monitoring plant performance under stress conditions. This review focuses on the use of chlorophyll fluorescence as a tool to study genetic variation underlying the stress tolerance responses to abiotic stress in A. thaliana.

Development of a Rapid Screening Method for Selection Against High Temperature Susceptibility in Garden Roses

The decline of garden rose sales over the past 20 years can be partially attributed to the lack of material adapted to a wide range of landscapes, which includes adaptation to high temperature stress. Current methods for evaluating high temperature susceptibility in garden roses are based on field observations, which are time consuming and subjected to ever-changing environmental conditions. A series of experiments were conducted to optimize protocols and compare the use of chlorophyll fluorescence (CFL) and cell membrane thermostability (MTS) by way of electrolyte leakage as methods to screen for high temperature susceptibility. Immature leaves proved better than mature leaves for both CFL and MTS measurements, using either detached leaf or whole plant stress assays. MTS measured on immature leaves stressed in a water bath at 50 °C for 45 minutes proved most consistent in separating rose clones based on high temperature susceptibility. Stressing actively growing plants with flower buds of 2 mm in diameter in a heat chamber at 44 °C for 3 hours resulted in increased flower abscission and leaf necrotic lesions on more susceptible clones when compared with those that were heat tolerant. Combining MTS measurements from immature leaves stressed in a water bath with the flower abscission and leaf necrosis responses 10 days after stress in a heat chamber could be the first step to screen and select against the more susceptible clones in a garden rose breeding program. Power analyses suggest that the proposed MTS protocol would be efficient in detecting differences between clones when the difference in electrolyte leakage is greater than 10%.

Use of chlorophyll fluorescence and P700 absorbance to rapidly detect glyphosate resistance in goosegrass (Eleusine indica)

The rapid detection of glyphosate resistance in goosegrass (Eleusine indica) will enhance our ability to respond to new resistant populations of this major weed. Chlorophyll fluorescence (Fluo) and P700 (reaction center chlorophyll of photosystem I) absorbance were analyzed in one biotype of goosegrass that is resistant to glyphosate and in another that remains sensitive to the herbicide. Both biotypes were treated with a foliar spray of glyphosate. Differences in photosystem II maximum quantum yield (Fv/Fm), effective photochemical quantum yield (Y(II)), and non-photochemical quenching (NPQ) between the biotypes increased over time. Values for Fv/Fm and Y(II) differed between the two biotypes 24 h after treatment (HAT). Differentiated activities and energy dissipation processes of photosystem II (PSII) and energy dissipation processes of photosystem I (PSI) were manifested in the two biotypes 24 HAT with 20 mmol L−1 glyphosate. Differentiated energy dissipation processes of PSI were still apparent 24 HAT with 200 mmol L−1 glyphosate. These results indicate that the Fluo parameters related to PSII activity and energy dissipation and the P700 parameters related to energy dissipation are suitable indicators that enable rapid detection of glyphosate resistance in goosegrass.

Use of in vivo chlorophyll fluorescence to estimate photosynthetic activity and biomass productivity in microalgae grown in different culture systems

In vivo chlorophyll fluorescence associated to Photosystem II is being used to evaluate photosynthetic activity of microalgae grown in different types of photobioreactors; however, controversy on methodology is usual. Several recommendations on the use of chlorophyll fluorescence to estimate electron transport rate and productivity of microalgae grown in thin-layer cascade cultivators and methacrylate cylindrical vessels are included. Different methodologies related to the measure of photosynthetic activity in microalgae are discussed: (1) measurement of light absorption, (2) determination of electron transport rates versus irradiance and (3) use of simplified devices based on pulse amplitude modulated (PAM) fluorescence as Junior PAM or Pocket PAM with optical fiber and optical head as measuring units, respectively. Data comparisons of in vivo chlorophyll fluorescence by using these devices and other PAM fluorometers as Water- PAM in the microalga Chlorella sp. (Chlorophyta) are presented. Estimations of carbon production and productivity by transforming electron transport rate to gross photosynthetic rate (as oxygen evolution) using reported oxygen produced per photons absorbed values and carbon photosynthetic yield based on reported oxygen/carbon ratio are also shown. The limitation of ETR as estimator of photosynthetic and biomass productivity is discussed. Low cost:quality PAMs can promote monitoring of chlorophyll fluorescence in algal biotechnology to estimate the photosynthetic activity and biomass productivity.

Spinach seed quality: potential for combining seed size grading and chlorophyll fluorescence sorting

AbstractSpinach (Spinacia oleracea L.) seed quality is important for subsequent establishment of baby leaf and other spinach products. The indeterminate flowering pattern in spinach produces seeds of different sizes, and consequently a non-uniform seed lot. Sorting seeds based on novel sorting methods might therefore improve the establishment of spinach for producers. Spinach seeds were harvested at five different times (H1, H2, H3, H4 and H5) starting 3 weeks before estimated optimum harvest time. The harvested seeds were sorted according to chlorophyll fluorescence (CF) and seed size. Two harvest times 6 d apart were selected for further studies of seed development and germination counts. Analysis of mean germination time (MGT) of four germination counts (3, 7, 14 and 21 d) showed that smaller seed sizes ( < 3.25 mm) have lower MGT than seeds of larger sizes (>3.25 mm). A larger proportion of 2.5–3.25 mm size seeds had germinated on day 3 than both their larger and smaller counterparts at the later time of harvest (H4). Seeds with a diameter below 2.5 mm displayed the lowest MGT. Commercially, the use of chlorophyll fluorescence (CF)-sorted seeds, in combination with seed size sorting, may provide a useful tool for enhancing seed quality. Here our results demonstrate that a greater number of seeds with a low CF level had germinated on day 3 compared to the seeds with high CF levels. It is of relevance to develop a technology that could identify seeds that are sufficiently developed to germinate and successfully establish in the field regardless of seed size.

Glyphosate uncouples gas exchange and chlorophyll fluorescence

Changes in chlorophyll fluorescence have often been advocated as a sensitive biomarker of plant stress, assuming that any kind of plant stress serious enough to affect plant growth will also affect photosynthesis. Glyphosate affects photosynthetic electron transport indirectly by inhibiting sink processes. The question is how fast this inhibition can be observed on CO(2) assimilation and ultimately on chlorophyll fluorescence? Experiments measuring CO(2) assimilation, conductance and chlorophyll fluorescence using four Kautsky curve parameters on barley (Hordeum vulgare L.) exposed to increasing doses of glyphosate showed a total cessation of CO(2) fixation and conductance without significant changes in chlorophyll fluorescence. The decrease in CO(2) fixation and conductance was significant 1 day after spraying and corresponded well to the decrease in biomass 5-7 days after spraying. A total cessation of CO(2) assimilation can take place without affecting chlorophyll fluorescence. Hypotheses concerning what happens to the energy from the photosynthetic apparatus that is not used for CO(2) assimilation are discussed. The results question the use of chlorophyll fluorescence as a universal indicator of stress on photosynthetic processes. Also, they demonstrate that changes in gas-exchange parameters are more sensitive biomarkers for glyphosate toxicity compared with chlorophyll fluorescence.

Can gypsophytes distinguish different types of gypsum habitats?

From an ecological point of view, gypsum outcrops and their corresponding vegetation are not yet fully understood. Most of the studies have concentrated on merely describing these plant communities. However, some researchers have tried to differentiate between these scrublands not only in terms of their geographical location, but also in terms of their ecological behaviour. Our botanical, edaphic and ecophysiological study, which adopts this last approach, makes use of chlorophyll fluorescence to distinguish the small—sized and sparse scrublands growing on gypsum barrens from the very different shrublike Ononis tridentata communities in the gypsum outcrop of the karst in Sorbas (Almería, Spain). In the three gypsophytes used to measure chlorophyll fluorescence values (Gypsophila struthium, Helianthemum squamatum and Teucrium turredanum), the records reveal that the environment has an impact on the Fv/Fm minimum values, however different the reaction of the species may be.

Chlorophyll Fluorescence: A Probe of Photosynthesis In Vivo

The use of chlorophyll fluorescence to monitor photosynthetic performance in algae and plants is now widespread. This review examines how fluorescence parameters can be used to evaluate changes in photosystem II (PSII) photochemistry, linear electron flux, and CO(2) assimilation in vivo, and outlines the theoretical bases for the use of specific fluorescence parameters. Although fluorescence parameters can be measured easily, many potential problems may arise when they are applied to predict changes in photosynthetic performance. In particular, consideration is given to problems associated with accurate estimation of the PSII operating efficiency measured by fluorescence and its relationship with the rates of linear electron flux and CO(2) assimilation. The roles of photochemical and nonphotochemical quenching in the determination of changes in PSII operating efficiency are examined. Finally, applications of fluorescence imaging to studies of photosynthetic heterogeneity and the rapid screening of large numbers of plants for perturbations in photosynthesis and associated metabolism are considered.

Use of chlorophyll fluorescence as a tool for determination of herbicide toxic effect: Review

Chlorophyll fluorescence-based methods have been used for many years to study the effect of environmental factors (including herbicides) on plants, and, with the development of very sensitive fluorometers, these methods have become very useful in ecotoxicological studies. This review provides a summary of the research done over the last 10 years concerning the study, by using chlorophyll fluorescence, of the herbicide toxic effects. Although numerous parameters are available, it is striking to notice that the majority of the studies done in the recent years used only a limited number of parameters, thus restraining in some way the interpretation of the obtained results. Furthermore, the use of the maximal photosystem II quantum yield to evaluate toxic effect of herbicides is probably not the best parameter due to its relatively low sensitivity. One should take the advantage of using other parameters such as the operational PSII quantum yield and the non-photochemical quenching since they integrate the entire physiological state of the plant and therefore should be more sensitive. We also recommend the systematic determination of EC50 values in future studies since such determination will permit a more accurate comparison between published reports.

Can photosynthesis-related parameters be used to establish the activity of acetolactate synthase–inhibiting herbicides on weeds?

The application of the acetolactate synthase (ALS)–inhibiting herbicide metsulfuron on greenhouse- and field-grown black nightshade and greenhouse-grown ladysthumb resulted in progressive inhibition of the level of carbon dioxide (CO2) fixation, the relative quantum efficiency of electron transport through photosystem I (ΦPSI) and II (ΦPSII), and the leaf chlorophyll content. Photosynthetic-related measurements, measured 2 to 4 d after treatment (DAT) at photon flux densities of 400 to 500 μmol m−2 s−1, provided valuable information before the visual symptoms that first appeared at 7 to 10 DAT with the herbicide. Measurements of the quantum efficiency for electron transport by photosystem II and the loss in leaf chlorophyll content appeared to be two of the most practical parameters to use when designing an early detection method to assess the toxicity of metsulfuron. The use of chlorophyll fluorescence would require a comparison of steady-state ΦPSII measurements for control and treated plants, which could be realized by either measuring in time (before/after application) or space (treated/untreated patch).

The use of chlorophyll fluorescence for monitoring photosynthetic condition of two tank-cultivated red macroalgae using fishpond effluents

In vivo chlorophyll fluorescence measured by pulse amplitude modulated (PAM) fluorometry was used as an indicator of photosynthetic activity in tank-cultivated red algae wGracilaria cornea and Asparagopsis armata (tetrasporophyte phase, previously known as Falkenbergia rufolanosa)x using effluent seawater from sea bream fishponds (Sparus aurata). Optimal quantum yield of indoorgrown G. cornea did not change during the period analysed (2 months). In contrast, optimal quantum yield decreased drastically in algae transferred from indoor to outdoor conditions. Maximal electron transport rate increased and photosynthetic pigments decreased in algae growing outdoors, indicating an acclimation to high irradiance. After 16 days, chlorophyll fluorescence decreased drastically and recovered partially when algae were transferred again from outdoor to indoor conditions. Falkenbergia rufolanosa was grown at three different biomass densities (4, 6 and 8 g l -1 ). The effects of three consecutive air compressor failure events on the photosynthetic activity were followed. An apparent degradation of the physiological conditions of the algae (resulting in their bleaching) was observed, concomitant with a strong decrease in the optimal quantum yield. This decrease was higher at algal biomass densities of 4gl -1 than at 6 or 8 g l-1. Three days after transfer to optimal conditions, i.e., normal aeration conditions, optimal quantum yield reached values around 0.50–0.55, close to the values before stress conditions. The results revealed that the use of chlorophyll fluorescence is a powerful means to rapidly detect different stress situations in integrated cultivation of seaweeds using fishpond effluents. In particular, the optimal quantum yield of algae can be monitored regularly as an early warning of the physiological stress in cultures.